Instead, by directly imaging
the layering and measuring the
fluid viscosity, the physicists
observed that, although the
amount of layering and delayer-
ing was comparable, the
changes in viscosity were sub-
stantially different in the thin-
ning and thickening regimes.
Because delayering occurred at
shear rates much lower than
those leading to thickening,
they proved that layering is not
the major reason for viscosity
changes in these suspensions.
The findings were published
in the Sept. 2 issue of Science
talline material, or porous coordination
polymer (PCP), transforms in accordance
with changes in its environment. Once
infused with distyrylbenzene (DSB), a
fluorescent reporter molecule, the composite becomes sensitive specifically to CO2
and glows with an intensity that correlates
to the concentration of that gas.
The scientists set out to see whether
their composite could differentiate between carbon dioxide and acetylene, a
compound with similar physiochemical
properties. They discovered that their
PCP-DSB combination reacted very differently to the two gases, which confirmed
that it could make accurate CO2 detection
possible in a variety of applications.
DSB exists as a long, flat molecule in
Gas detector lights up around CO2
KYOTO, Japan – An inexpensive new
material can quickly and accurately detect
carbon dioxide (CO2) under a variety of
circumstances, enabling the development
of easy-to-use CO2 monitors.
Methods to detect whether specific
gases are present in the air already exist,
but they come with many drawbacks,
including high energy cost, slow detection
speed, large size and sensitivity to humidity. Now, Kyoto University scientists have
developed an inexpensive, reusable compound that gives off variable degrees of
visible light that correspond to gas concentrations.
Their findings, published online Sept. 4
in Nature Materials (doi: 10.1038/nmat
3104), describe how the flexible crys-
its natural state, and it emits blue light.
However, when absorbed by the PCP
framework, DSB molecules twist, causing
the PCP structure to become skewed
and the glow of DSB to diminish signifi-
cantly. They observed that the presence of
CO2 causes the DSB molecules to revert
to their flat, brightly fluorescent form,
while also returning the PCP grid to its
usual state. These steps could be reversed,
however, without causing any significant
changes to the composite.